class Container {
  final int width;
  final int height;
  //常量构造函数
  const Container({required this.width, required this.height});
}

void main(List<String> args) {
  var c1 = Container(height: 100, width: 100);
  var c2 = Container(width: 100, height: 100);
  print(identical(c1, c2));

  // const 必须是常量构造函数
  var c3 = const Container(height: 100, width: 100);
  var c4 = const Container(width: 100, height: 100);
  print(identical(c3, c4));
}
